Medical injector



Nov. 10, 1964 D. E. WILLIAMSON MEDICAL INJECTOR 2 Sheets-Sheet 1 Filed D80- 7. 1961 INVENTOR. jazzahj Walkaway/p BY Maw/2% rr'yf Nov. 10, 1964 D. E. WILLIAMSON MEDICAL INJECTOR 2 Sheets-Sheet 2 Filed Dec. 7, 1961 United States Patent 3,156,236 MEDICAL INJECTOR Donald E. Williamson, Miami, Fla, assignor to Cordis Corporation, Miami, Fla, a corporation of Florida Filed Dec. 7, 1961, Ser. No. 157,792 9 Claims. (6!. 1.28-2.05)

This invention relates to hydraulic injection devices for medical purposes and more particularly to such devices as will provide a controllable, uniform injection pressure suitable for use in angiocardiography, which involves the injection of radio opaque contrast medium into the vascular system through a thin flexible tube lmown as a catheter, and the observation of the propagation of these materials by means of X-ray photography. In the injection of the radio opaque materials it is necessary to produce controlled pressures from near zero to 800 or 1000 pounds per square inch. This pressure is required in the contrast medium injector in order that a sufficient quantity of liquid will flow .through the long thin catheter leading from the injector to the site of the injection, which may be in a vein, artery or in the heart itself. The beginning of injection must be controllable, and the build-up of pressure must be practically instantaneous so that the injection can be timed with a certain cycle of a heart beat. Likewise, the end of the injection must also be controllable. Various types of drives have been devised for hydraulic cylinders in order to produce these pressures. Among these are spring driven, pneumatically driven and hydraulically driven devices.

Objects of .the present invention are to provide an electrically driven source of hydraulic pressure which may be so controlled as to be suitable for use in angiography. Further objects are to provide such a hydraulic pressure source which will produce a uniform pressure over an entire injection procedure, which may be easily changed from one pressure to another, and which permits the duration and timing of the pressure cycle to be easily controlled. Still further objects are to provide such apparatus which includes provision for indicating externally the beginning and end of the pressure cycle and provision for easily refilling the apparatus with injection medium.

In that an injection device of the character contemplated almost necessarily involves a piston and cylinder arrangement for operating upon the injection medium, a linear electric motor such as a solenoid would seem to be indicated. However, the force developed by a solenoid is both difficult to regulate and is highly dependent upon the position of the moving member so that a stroke of uniform force throughout its length is extremely ditficult to obtain. The present invention therefore contemplates using a rotary electric motor as a constant torque producing device, in contrast to its usual power producing function, and then converting the rotary motion to a linear movement appropriate for operating a hydraulic piston and cylinder.

In a particular embodiment, a permanent split capacitor induction motor is employed to produce constant torque by operating the motor in an overloaded mode at speeds substantially below synchronous speed. So operated, a permanent split capacitor induction motor will produce reasonably constant torque over an appreciable speed range. ation of such motors with small amounts of slip, that is at speeds close to the synchronous speed, in which there are large variations in torque with small changes in speed.

In a more particular aspect the invention also involves a ball-nut for efiiciently converting rotary-motion to linear motion, a hydraulic piston and cylinder means, andmeans for applying alternating electric current of a predetermined potential to the motor, said potential being adjustable for adjustirn the torque level.

This is incontrast to the normal mode or oper 3,15%,23h Fatented Nov. 10, 1964 For the purpose of illustration a preferred embodiment of the invention is shown in the accompanying drawings in which FIG. 1 is a side elevation of a hydraulic injector;

FIG. 2 is a section on the line 2-2 of FIG. 1;

FIG. 3 is a section on the line 33 of FIG. 1;

FIG. 4 is a schematic representation of control circuitry for operating .the injector of FIG. 1; and

FIG. 5 is an enlarged view of the clutch assembly included in FIG. 1.

Referring now to the drawings the mechanical components of the injector are mounted on a two-piece offset frame 10, the two components of the frame 12 and 14 being joined by bolts 16. A permanent split capacitor induction motor 20 is mounted on the frame and drives a ball-nut device 22 through a combination slip clutch and thrust bearing assembly 24.

The ball-nut device 22 involves a threaded shaft 26 as well as the ball-nut proper 28 which operates in engagement therewith. The threaded shaft 26 is connected with the shaft of the motor 20 through the slip clutch assembly 2 When the threaded shaft 26 is rotated by the motor 24) the ball-nut 28 cooperates with the threaded shaft 26 to transform the rotational movement into linear displacement in the same manner as a conventional nut, but with much greater efficiency, efficiencies of being easily obtainable. Because of the high efficiency of the ball-nut as contrasted with a conventional nut, a constant torque can be transformed into a constant or uniform thrust without distortion due to friction losses.

The ball-nut drives a hollow push tube 30 within which the threaded shaft 26 nests before the injection stroke. The push tube and ball-nut are prevented from rotating with the shaft 26 by a tail piece 32 which engages a corresponding slot 34 in the frame component 12. The front end of this push tube slides in a pillow block 36 having a nylon bushing 4t and attached to the frame member 12 by the screws 38.

The thrust created by the ball-nut device 22 is, of course, transmitted back through the shaft 26 to the motor 20. The slip clutch assembly 24 is particularly designed to both transmit this thrust and to provide a slip action for limiting the torque which may be applied by the motor to the ball-nut device 22. The body of the assembly 24 is constructed in two parts, the forward one of which 42 is secured to the threaded shaft 26 by the set-screw 44. The rearward portion of the body 4-6 is secured to the shaft 48 of the motor 20 by the set screw 49. The two body parts are joined by a single row ball bearing 56 whose inner and outer races are secured to the forward and rearward body parts respectively by the clamp rings 52 and 54 and the cap screws 56 and 53.

The forward body part 2-2 has a felt bearing surface 62 and torque is transmitted through the assembly 24- by a clutch plate 60 which bears against the felt surface 62 and which is prevented from rotating relative to the rearward body part 46 by engagement with the heads of the cap screws 56. Friction force is provided by coil springs 64 which rest against torque adjustment set screws 66 spaced around me periphery of the rearward body part 46.

A fitting 7%) is secured to the front end of the push tube 39 by screws 72 and isadapted to releasably engage the shaft head 74 of aconventional injection cylinder 76. The cylinder 76 is held in an open-top box member 78 which is attached to the frame 12. As may be seen from FIGS. 1 and 2 the cylinder may thus be removed from the injector for cleaning and for filling simply by lifting it upward thereby disengaging it both from the box 78 and the fitting 70.

As stated earlier, it is typically a requirement for satisfactory angiocardiography that the pressure of injection of the radio opaque medium be constant during injection and be precisely controllable. To meet this requirement the present invention contemplates that the motor be operated as a constant torque motor in an overloaded mode in contrast to its normal mode at speeds near synchronous speed.

When used normally, induction motors conventionally operate with a small amount of slip and the speed of the motor varies only slightly with relatively large variations in torque load. Stated conversely, the available torque varies widely with small changes in speed. However, when the motor 20 is operated at speeds substantially slower than its synchronous speed, the motor has the characteristic of producing essentially constant torque over a quite wide range of speeds. This torque level is determined largely by the potential of the alternating current supplied to the motor. By operating the motor in this mode and by using the highly efficient ball-nut device 22 to transform the constant torque into constant thrust, a source of uniform thrust is obtained which may be utilized by the cylinder '76 to produce a uniform hydraulic injection pressure. Further, this uniform pressure may be easily adjusted by controlling the potential of the electric current supplied to the motor, as, for example, by a tapped autotransformer.

Circuitry appropriate for controlling the motor 20 is shown in FIG. 4. Power for the apparatus is provided to fused leads 100 which are arranged to take 110 volt alternating currernt power from the terminals 102. A tapped autotransformer 104 has its input connected across the leads 1% and is arranged so that when the switch S1, having sections Sta, S111 and Sic, is in the position shown and the relay contacts RYI are closed, alternating current power at a potential determined by the setting of the autotransformer variable tap 106, is supplied to the motor Zil through the terminals Hi? and 111. These terminals correspond to an internal connection of the motor 2t? appropriate for normal speed forward operation. As indicated previously, the hydraulic pressure developed by the injector is dependent upon the voltage applied to the motor 20 and thus also upon the setting of the variable tap 106. Further, for a given setting of the tap, the pressure remains essentially uniform throughout the injection process.

With the various switches in the positions shown in FIG. 4, the timing of the injection process is accomplished by means of the relay contacts RYE and the operation of these relay contacts is in turn controlled by the operation of the push button P1 in the following manner. With the switch section Sta in the position shown, one side of the push button Pi is connected to one of the leads Mitt. Similarly, power is supplied to the neon bulb NEE, the lighting of which indicates that the apparatus is electrically ready for an injection. Depressing the push button completes a circuit to the other lead 1% through the limit switches L1 and L2 and through the relay coil RY. The limit switches L1. and L2 (not shown in FIG. 1) are arranged to be operated by the tail piece 32 when the push tube is in the most forward and rearward portions respectively of its travel. Energizing the coil RY closes the relay contact RYl.

Energizing the coil RY also closes the contacts RY2 thereby causing the electrolytic condenser C1 to be charged through the rectifier D1 and the current limiting resistor R1. At the end of the injection process the motor is disconnected from its source of alternating current power by the opening of the relay contacts RYZ'l and is simultaneously connected across the charged capacitor C1 by the closing of the normally-closed relay contacted RYE. This latter connection causes a heavy surge of direct current power to pass through the motors coils. This surge, by the induction of strong eddy currents in the motors rotor, brings the motor to a nearly instantaneous stop. This feature prevents the overrunning of the injection process which might otherwise be caused by the momentum of the various rotating parts. For a motor 2% of A HP. rating appropriate values for R1 and C1 are 10 ohms and 4 2000 microfarads, respectively. The diode D1 can be of the semi-conductor type IN 1345.

So that the injector may be returned to its original position and so that the cylinder 76 may be filled and cleared of bubbles while in place on the injector, it is preferable that the motor 20 be of a type which is operable at less than full power. For example if the motor 20 normally operates as a four pole motor it is desirable that there also be within the motor internal connections for permitting its operation as a twelve pole device, such a provision being capable of reducing its operating speed by a factor of three. Similarly it is desirable that the motor be operable in this mode in either the forward or the reverse direction. The internal connections of the motor necessary for such speed changes and reversals of direction are indicated in FIG. 4, by the terminals 119-114. The terminal is common to all of the motors windings and the terminal 111 represents the full speed or four pole connection in the forward direction as stated previously. The terminal 112 (unused) represents the four pole connection for the reverse direction. The twelve pole connections for the forward and reverse directions are brought out to the terminals 113 and 114 respectively. The phase-shifting capacitors which determine the direction of rotation for the fast and slow speeds are indicated at C2 and C3 respectively.

The choice of mode, whether four pole or twelve pole, is determined by the setting of the switch S1. The determination of which direction and the actual initiation of movement is accomplished by the three-pole double-throw momentary-contact switch S2 whose three sections are designated S212, S212 and S20. Reversing the position of the switch section Sla from the position shown in FIG. 3 permits the switch section 82a to assume, by its operation in either direction, the function of the push-button Pi, that is to actuate the relay coil RY. Switch section S11) disconnects the variable autotransformer tap 106 and connects in its place a fixed low voltage tap 168 so that the torque capabilities of the motor 20 in its twelve pole configuration are held to a low level. The reversal of the switch section Sic permits the connection of the autotransformer to the twelve pole terminals 114 and 116 in place of the four pole terminal 112.

Operation of switch S2 in the downward direction as shown in FIG. 4 causes the motor 22 to revolve in the forward direction and movement of the switch upwardly causes the motor to rotate in the reverse direction. As indicated previously, the closing of the relay contacts RYT may be brought about the operation of the switch section 82a in either direction. The switch section 82b permits the relay to be operated even though one of the limit switches L1, L2 is open provided that limit switch is at that end of the push tubes travel from which movement is then being initiated. Finally, the operation of the switch section S20 chooses in which direction the motor is to operate by determining which of the terminals or 116 receives normal phase power.

in that it is typically desirable to time X-ray exposures from either the beginning or end of the injection cycle the circuitry shown in FIG. 4 includes provision for indicating externally the happening of either of those events. For this purpose a one ohm resistor R2 is placed in series with the capacitor C1. A pulse is generated across this resistor at both the beginning and end of the injection cycle. The pulse at the beginning of the injection cycle is a positive one caused by the charging of capacitor C1 upon the closing of the relay contacts RYZ. The pulse at the end of the injection cycle is a negative one caused by the discharge of the capacitor through the motor windings. For operating associated electronic equipment the pulses are made available to external apparatus through the terminals 115 and, for convenience in the operation of such associated electronic apparatus, the relative polarity of the pulses can be reversed by means of the DPDT switch S3 and the unneeded pulse is blocked by the operation of the semi-conductor diode D2. "To prevent the unintended tripping of X-ray apparatus the switch Sld prevents the passage of any pulses when the motor 2%) is being operated in its twelve pole configuration;

It should be understood that this disclosure is for the purpose of illustration only and that the present invention includes all modifications and equivalents falling within the scope of the appended claims.

I claim:

, 1. An injection device for providing constant hydraulic pressure suitable for angiography injections comprising: a constant torque electric motor; means for efficiently converting the constant torque available from said motor to constant thrust; and a hydraulic piston and cylinder, the piston of which is driven by said means whereby energization of said motor to produce constant torque will provide constant pressure in a hydraulic medium contained in said cylinder.

2. An injection device according to claim 1 further comprising means for applying electric current of a predetermined, selectable potential to said motor.

3. An injection device according to claim 1 in which said means includes a threaded shaft and a ball-nut.

4. An injection device according to claim 3, further comprising a thrust-transmitting slip clutch interposed between said motor and said converting means.

5. An injection device according to claim 4, in which said slip clutch includes a thrust bearing and, in mechanical parallelism therewith, a pair of preload friction surfaces.

6. An injection device according to claim 4, in which said slip clutch includes a first rotatable element having a friction surface, a second rotatable element, a thrustbearing interposed between said rotatable elements, a friction element, and means for causing said friction element to rotate with said second rotatable element and to be resiliently urged against said friction surface.

7. An injection device for providing constant hydraulic pressure suitable for angiography injections comprising: a permanent split capacitor induction motor; means for efi'iciently converting the torque available from said motor to axial thrust; a hydraulic piston and cylinder, the piston of which is driven by said means; means for applying alternating electric current to said motor of a predetermined potential such that said motor will operate in a constant torque mode, whereby energization of said motor to produce constant torque will provide constant pressure in a hydraulic medium contained in said cylinder.

8. An injection device according to claim 7 further comprising means for applying direct current to said motor following the application of alternating current, for bringing said motor to an abrupt stop.

9. An injection device according to claim 8 in which the means for applying a direct current to said motor includes a capacitor and means for charging said capacitor while alternating current is applied to said motor, and for discharging said capacitor through the windings of said motor when the application of alternating current is terminated.

References Cited in the file of this patent UNITED STATES PATENTS 2,466,772 Kenyon Apr. 12, 1949 2,602,446 Glass July 8, 1952 2,627,270 Glass Feb. 3, 1953 2,702,547 Glass Feb. 22, 1955 2,734,504 rescas Feb. 14, 1956 2,779,336 Abbe Jan. 29, 1957 2,786,468 Singer Mar. 26, 1957 2,976,865 Shipley Mar. 28, 1961 FOREIGN PATENTS 28,796 Great Britain Dec. 13, 1913 745,957 France Feb. 27, 1933 458,275 Italy July 4, 1950 OTHER REFERENCES Marks: Mechanical Engineers Handbook, Fourth Edition, 1941, pp. 941, 1457. 

1. AN INJECTION DEVICE FOR PROVIDING CONSTANT HYDRAULIC PRESSURE SUITABLE FOR ANGIOGRAPHY INJECTIONS COMPRISING: A CONSTANT TORQUE ELECTRIC MOTOR; MEANS FOR EFFICIENTLY CONVERTING THE CONSTANT TORQUE AVAILABLE FROM SAID MOTOR TO CONSTANT THRUST; AND A HYDRAULIC PISTON AND CYLINDER, THE PISTON OF WHICH IS DRIVEN BY SAID MEANS WHEREBY ENERGIZATION OF SAID MOTOR TO PRODUCE CONSTANT TORQUE WILL PROVIDE CONSTANT PRESSURE IN A HYDRAULIC MEDIUM CONTAINED IN SAID CYLINDER. 